1. Field of the Invention
This invention relates to separation of a multicomponent mixture into the components thereof by means of adsorption.
More specifically, the present invention relates to a method and to an apparatus for separation of a multicomponent mixture into the components thereof by means of adsorption where use is made of a plurality of columns each having an adsorbent packed therein which is capable of selectively adsorbing each of the component and where an effluent from one of the columns is used as a fluid for purifying the adsorbate in another column whereby separation of the components is made by a desorbent in a minimum amount so that each adsorbate is desorbed in a higher concentration, in a higher purity and in a higher recovery efficiency.
2. Related Art
Heretofore, techniques such as gas chromatography and liquid chromatography utilizing the difference in distribution coefficient against adsorbents have been known as means for separating and purifying components in a multicomponent mixture.
These separation/purification means have excellent separation ability and therefore they have been widely used in chemical analysis of complex mixtures. However, when these means are used as separation/purification means on an industrial scale, the purification cost is high due to batch operation. Accordingly, the application fields of such means are limited. In addition, the components separated as adsorbates may not be recovered since they are small in quantity whereby the separation of components through adsorption may have thus been used solely as a means for chemical analysis.
On the other hand, in a pseudo-moving bed adsorption separation apparatus wherein continuous operation is used on an industrial scale such as continuous separation apparatus described in U.S. Pat. No. 2,985,589, a mixture containing 2 components is separated. However, it may, as long as we know, be difficult to continuously separate a mixture containing at least 3 components by a single apparatus.
In a process for continuously separating 3 components by a pseudo-moving bed adsorption separation apparatus recently proposed in Japanese Patent Laid-Open Publication No. 80409/1989, the separation has been realized by alternately disposing a column packed with a first packing wherein its distribution coefficient against Components A, B and C is Component A&lt;Component B&lt;Component C and a column packed with a second packing wherein its distribution coefficient is Component A&lt;Component C&lt;Component B and flowing the solution through the columns.
However, these methods may be restricted to operations in that fluid flows through each column and one-column based operation may decrease an efficiency in returning an effluent from a column to another column, a long time may be needed until stabilization of operations is reached and a long time may also be required until the amount and purity of an adsorbate reach at an elevated level. These methods could, as long as we know, entail increase in cost or difficulty in their applicability to operation in a small quantity.
We have also proposed a method of separation in Japanese Patent Application No. 15882/1991, which is equivalent to U.S. patent application Ser. No. 114,331. Our method proposed is assumed to be improved over some of the prior art method, but would be further improved if the amount of a desorbent is decreased. More particularly, the method we proposed may require a relatively large amount of a desorbent, whereby a relatively large volume of an apparatus for practicing the method may be required resulting in relatively large amounts of a facility cost and of a running cost.